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Large Intestine

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Large Intestine

Liquid to solid. What does this mean?

Well, that's exactly what the large intestine does. It takes the remains of digested food — that is, food in which all the nutrients and minerals have been removed, and prepares it for elimination.

The Large Intestine and Its Functions

From the small intestine, any remaining food wastes pass into the large intestine. The large intestine is a relatively wide tube that connects the small intestine with the anus. Like the small intestine, the large intestine also consists of three parts: the cecum (or caecum), colon, and rectum. Follow food as it moves through the digestive system at http://www.youtube.com/watch?v=Uzl6M1YlU3w (1:37).

The digestive system song "Where Will I Go" can be heard at http://www.youtube.com/watch?v=OYWVbt6t2mw (3:27).

The following interactive animation demonstrates how the gastrointestinal (GI) system eliminates waste.

Absorption of Water and Elimination of Wastes

The cecum is the first part of the large intestine, where wastes enter from the small intestine. The wastes are in a liquid state. As they pass through the colon , which is the second part of the large intestine, excess water is absorbed. The remaining solid wastes are called feces . Feces accumulate in the rectum , which is the third part of the large intestine. As the rectum fills, the feces become compacted. After a certain amount of feces accumulate, they are eliminated from the body. A sphincter controls the anus and opens to let feces pass through.

Bacteria in the Large Intestine

Trillions of bacteria normally live in the large intestine. Most of them are helpful. In fact, we wouldn’t be able to survive without them. Some of the bacteria produce vitamins, which are absorbed by the large intestine. Other functions of intestinal bacteria include:

  • controlling the growth of harmful bacteria.
  • breaking down indigestible food components.
  • producing substances that help prevent colon cancer.
  • breaking down toxins before they can poison the body.

Summary

  • The absorption of water from digestive wastes and the elimination of the remaining solid wastes occur in the large intestine.
  • The large intestine also contains helpful bacteria.

Practice

Use this resource to answer the questions that follow. Use this resource to answer the questions that follow.

  1. What is the main function of the large intestine?
  2. How does the large intestine conserve water?
  3. In addition to water, what other compounds are reabsorbed by the large intestine?

Review

1. Describe the functions of the three parts of the large intestine.

2. How do bacteria in the large intestine help keep us healthy?

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